Fixing boxes to a tanked wall.

[ban-all-sheds]

The problem is that neither you, nor, it seems likely, your customer, are experts in tanking basements. If we assume that the sockets are 2m below ground level, what's the potential hydrostatic pressure of groundwater at that point?

Basements cost a lot to build, not because their builders drive to work in fur-lined Rolls-Royces, but because they are tricky to get right.

tanked walls are always a nightmare and any answers and subsequent problems could lead you into expensive "it's your fault" arguments in a year's time.

Concur with that. They will normally advise what they want done. You don't want to make it up yourself.

Not easy, but I'd suggest telling him that boxes have to be surface mounted or you won't do it. Sounds dramatic, but I have seen cases where tanking has failed or has been the wrong solution and when problems arise the tradesmen working inside the building have been blamed by the householder or their insurance company. Even where it was shown that the problem had been caused by a DPC in the wrong place, it still cost the builder a small fortune in solicitor's costs, time on site, lost work etc. TBH the whole concept sounds a bit dubious. Tanking has to have a certain amount of flexibility and yet he's using dot and dab. As others have said there are lots of problems with condensation, salts and movement. Protect your back. Maybe worth talking to the building inspector.

What they all said.

It's not being done by a tanking company. Basically a bloke who is building his own under build extension,

Be afraid.

 

[bernardgreen]

No I have chiseled out the block. He will now tank the bit which has been chiseled out.

Not a good situation

So it is internal tanking. Internal tanking is very difficult to repair, bonding new to old on a damp wall takes a lot of care and even then weeping leaks or total failure can occur.

If it is block work without external tanking then the blocks will be at best damp and at worse saturated.

 

[Martynrosscampbell]

I've had to do this a few times. Its understandable if the owner/ builder doesn't want to build a stud wall inside of the tanking. If nothing else it eats up space!

I used adhesive, think it was pink grip but there is better out there. Needs to be quite stiff and fast setting so the boxes don't slide down the wall as soon as you leave!! put the cables in oval conduit and stick that to the wall as well. If you have a flat block wall is shouldn't be too bad! I was doing it on old stone and cob walls.

Have plenty of bits of wood and heavy stuff around to prop the boxes and hold the pipe back.
There's no easy answer I'm afraid.
Good Luck

 

[Lectrician]

If it is dry lined, I guess there is nothing to stop you chomping out a sodding great hole for the box, a chase down it you wish, letting him tank the lot, then leaving your cables unfixed in the chase, and cutting dry lining boxes in (hence the oversized sodding great holes where the boxes go).

Your install then doesn't even really touch his.

I would disclaimer this in my quote.

 

[flyingsparks]

Dry lining boxes are possibly an option if I knock the block out deep enough yes your right, thanks. The wall itself is not damp to the touch, is not piled up with earth behind it on the outside, has a dpc and is a cavity wall, so really I don't know why it's being tanked. If it was actually wet, I think a lot of your responses would be more sensible approach. However considering it is actually very 'dry' I think sticking with sticks like s*hit the boxes in isn't going to be a problem this time. I will perhaps still disclaimer this tho. Good idea.